These tools are used in all machine shops everywhere, they are inexpensive and very useful and you can never have enough of them. The next step will involve heat treating to harden the steel so it can withstand some abuse without getting damaged. Most home machine shops or hobby mills are not able to make large parts so a 3” measuring range is perfect for most hobbyists. That guy, Mike Taylor, sells a kit of 6 hex-head screws, sized for 1″, 2″, and 3″ attachment, 4 threaded through-hole dowels, a hex key, and a slotted driver head — all housed in a handy little plastic case.

I suspect that the reason for the holes has been forgotten by manufacturers, the way most are made do not make it possible to connect them together. This hardware kits contains the following parts: two each 7/8 inch long by 5/16 inch diameter 8-32 threads dowels, two each 7/8 inch long by 5/16 inch diameter through hole dowels that fit 8-32 bolts, two each of the following length 8-32 Allen Head Cap Screws 1-1/2 inch, 2 inch and 2-1/2 inch, 9/64 inch hex key and a small flat screwdriver tip.The reason for the holes is to give you the ability to clamp them together to create elaborate setups, generally intended for inspection purposes I believe. I already gave my recommendation at the top of this article but to be honest you could buy most brands and still get a good set. Although the extra width when compared to a proper square can sometimes be an issue. Verifying Your Measuring tools I have used the threaded holes before for adding an additional small clamp or two for an awkward shaped casting.

Join over 36,000+ makers on Adafruit’s Discord channels and be part of the community! http://adafru.it/discord Multiple holes are drilled into them on each face, some of these holes are threaded, typically every other hole.